Explanation:
In low Earth orbit there is not
enough atmosphere
to diffuse and scatter sunlight,
so shadows are black and
the sky is
dark - even when the Sun shines.
The harsh lighting produced this
dramatic effect
as mission specialist Gregory Harbaugh
photographed colleague Joseph Tanner during
their second spacewalk to
service the Hubble
Space Telescope in February 1997.
The aft section of the
Space Shuttle Discovery is
visible in the background with
the Sun hanging over a delicate crescent of
the Earth's limb.
A checklist is attached to Tanner's left arm, and
Harbaugh's reflection
is just visible in Tanner's visor.